Gas sensors, in particular lambda sensors, generally have a housing through which the electrical connection cables for the sensor element must be fed on the front-side, for instance. The sensor element is contacted by the connection cables inside the housing. The gas sensors for determining the exhaust-gas composition in motor vehicles are installed in the exhaust pipe and thus are exposed to the environmental influences prevailing there. The sensor element situated inside the housing often must not come into contact with detrimental environmental influences such as dirt, oil and/or water. It is therefore necessary to provide sealing of the cable feedthrough both with respect to the housing and the cable insulation.
From German Published Patent Application No. 41 26 378 and also from German Published Patent Application No. 195 42 650, cable feedthroughs are known in which the connection cables are guided through an elastic, plug-type molded part and sealed. The molded part is made of a temperature-resistant material such as PTFE (Teflon) and is enclosed and compressed by a housing sleeve, which forms the housing. According to German Published Patent Application No. 41 26 378, for instance, an O-ring is additionally inserted for sealing between housing sleeve and molded part. The O-ring is made of an elastomer such as Viton and has only limited temperature resistance.
According to German Published Patent Application No. 195 42 650, a plug made of PTFE is provided, which is to ensure sealing not only with respect to the cables but with respect to the housing as well. A support ring is inserted in an annular groove of the PTFE plug for this purpose.
However, lately lambda sensors of the exhaust tract are being moved closer and closer to the engine in vehicle applications, so that the temperature loading of corresponding sensors has increased steadily. It has become apparent, however, that the cable feedthroughs according to the related art are unable to tolerate the temperature loading in very close proximity to the engine in the long term.